There are many methods, well known in the art, for preparing catalysts and electron donors, which can produce polypropylene polymers having high stereoregularity.
For example, U.S. Pat. No. 4,952,649 discloses a method for producing high stereoregular polypropylene with the isotacticity index (weight % of xylene insoluble part) of 96˜98%, by forming recrystallized solid catalyst particles from the reaction of magnesium chloride dissolved in 2-ethylhexyl alcohol with titanium tetrachloride and dialkyl phthalate at −20˜130° C., and using the resulted solid catalyst particles with triethyl aluminum as a cocatalyst and various types of alkoxy silanes as an external electron donor in bulk polymerization.
Further, according to U.S. Pat. No. 5,028,671, a method for preparing high stereoregular polypropylene with the isotacticity index of 97˜98% is disclosed, which method uses a mixture of a spherical solid catalyst, triethyl aluminum as a cocatalyst, and dialkyldimethoxy silane as an external electron donor, wherein the spherical catalyst is obtained by reacting a spherical ethanol-containing magnesium chloride carrier, which has been prepared by spray drying, with titanium tetrachloride and dialkyl phthalate.
The polypropylene prepared by the above-said methods shows high stereoregularity to a certain extent, however its activity is 30 kg-PP/g-cat or less which is considered to be not sufficient for the preparation of polypropylene having reduced catalyst residues as an environmentally-friendly material.